In reply to a post by b4dger:

That's why I wasn't happy with @RobertoS statement making it sound like customers would get 'clean' results if they had an engineer install - there's more to it than that...

Yes there is more to it than that. Be aware that the speed guestimator assumes you are within some short range of the DP, so if you are some distance from the DP the guestimator will be wrong.

My exact words were

Engineer installs are expected to give the Clean range figures, whereas self-installs are likely to give Impacted range.

Expected != Will.

Likely != Will.

I wasn't writing a book, for heaven's sake. Of course some will not, in both scenarios.

In reply to a post by b4dger:

That's why I wasn't happy with @RobertoS statement making it sound like customers would get 'clean' results if they had an engineer install - there's more to it than that...

I didn't say anything about the actual results achieved either.

However, there are two important tests that you have to get past if you want to report low speeds (without fault indications) to the ISP and to get an engineer out to investigate.

First your ISP must decide whether to accept your request for support. They will do this based on comparing your actual speed with one of the ranges ... either as-is, or as-was at the time of purchase. If you want them to choose the clean range for this comparison, then you are much more likely to have needed to get an engineer installation.

The FTTC handbook (for ISPs) includes Openreach's recommendation to quote range B estimates to potential customers, if they go for self-install. This initial quote affects the choices made by ISPs forever afterwards.

Second, Openreach must apply the same test before accepting the task. Their threshold used to be the bottom of the appropriate range (the 20th percentile), but nowadays their threshold is even lower - at the tenth percentile.

If you want action, and the attention of an engineer, then being able to use the clean range is of a benefit. Of course, having an engineer attend is not a guarantee of a fix.

Having said all of that, then if your line has a fault that can be detected by the automatic line testing equipment, both ISP and Openreach should respond to that. This kind of copper line condition is not an impediment.